Below, a conventional inertial force sensor is explained with reference to a drawing.
FIG. 8 is a perspective view of an oscillator used for a conventional inertial force sensor. In FIG. 8, the conventional inertial force sensor is a piezoelectric transducer type sensor composed of oscillator 1 and a circuit for detecting an inertia force on a basis of signal from oscillator 1. The oscillator 1 includes two tuning fork arms 2 and 3 facing each other and base 4 linking two tuning fork arms 2 and 3. For a convenience of explanation, x, y and z axes mutually crossing at right angles are shown in FIG. 8. Tuning fork arms 2 and 3 are designed to be oscillated in the x-axis direction. For tuning fork arms 2 and 3 to oscillate ideally in the x-axis direction, a cross section of each arm is desirably formed in a rectangular shape so that they constitute a detailed and accurate symmetry with regard to x-axis and z-axis. However, due to a variation on work process in producing oscillator 1, it is extremely hard to produce the arm precisely in a rectangular shape. For this reason, when the element is oscillated, an unwanted vibration signal is generated and superimposed on a principal oscillation in the x-axis direction.
In order to solve the problem, after oscillator 1 is finished, trimming slit 8 is formed on tuning fork arm 2 and 3 by radiating a laser on each of the arm and melt-removing a part of oscillator 1. A mass balance between arm 2 and 3 being adjusted in this manner, the element oscillates properly in the x-axis direction. In this arrangement, the trimming slit is formed on ridge portion 7 where melt-removing is easy. As prior art documental information relating to an application of this invention, Unexamined Japanese Patent Publication No. 2004-93158 is publicly known, for instance. However, in this conventional method, a work affected layer is possibly formed near trimming slit 8 of tuning fork arm 2 and 3 due to processing heat, dropping strength of base material and damaging tuning fork arm 2 and 3 or generating an undesired oscillation.